Fixed win32 build of tools

load(qt_parts) causes the inclusion of src, tools etc
but on non-win32 platforms (and wince and winrt) we have
to add the src subdirectory anyways in order to create
the doc target.

Task-number: QTBUG-46712
Change-Id: I51cf4050fed744c844acc8ff4fe5f5f1d8c32d1a
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

qtactiveqt.pro

@@ -3,5 +3,5 @@ load(qt_parts)
 
 !win32|winrt|wince {
     message("ActiveQt is a Windows Desktop-only module. Will just generate a docs target.")
+    SUBDIRS = src
 }
-SUBDIRS = src